How do I stop cam from moving during leak down test?

By bearscare, Posted May 14, 2011

Hi-

I've been trying to do a leak down test and when I pressurize the cylinder to 100 psi I can't get enough torque on the allen screw on the crank to pull the piston to TDC. How does anyone do these test without having the crank (piston) move?

By Shawn_Mc, Posted May 15, 2011

You need to stop the crank at TDC. If you try to use the cam chain you can end up hurting it. Lots of torque there multiplied by 2!

By bearscare, Posted May 17, 2011

I was going to use the motion pro tool to stop the cam gear. But you're right way too much torque for the chain and sprocket to endure. This weekend I removed the chain from the sprocket and let the piston go to BDC.

Why does the piston need to be TDC for this test? I put in 100 psi and lost 12 psi. That sounds pretty good to me.

Thanks

Bruce

By Wahoo214, Posted May 17, 2011

I was going to use the motion pro tool to stop the cam gear. But you're right way too much torque for the chain and sprocket to endure. This weekend I removed the chain from the sprocket and let the piston go to BDC.

Why does the piston need to be TDC for this test? I put in 100 psi and lost 12 psi. That sounds pretty good to me.

Thanks

Bruce

If you performed the test correctly, a 12% loss is significant. Think about it as losing 12% of your power.

By MELK-MAN, Posted May 17, 2011

If you performed the test correctly, a 12% loss is significant. Think about it as losing 12% of your power.

i wasn't sure when he said "lost 12psi" .. but that was kind of what i thought, 100psi in, 12psi loss, 12%... On inline 4 roadrace bikes we like to see 2% when fresh, 5% is good but top riders would be buying parts to get ready for refresh, 10% leak down is way time to do, unless your just streeting or track days.. Listen in the pipe while performing the test, if you hear hissing there.. it's getting by the valves. Im not familiar with where the crf motor would come out the bottom, but on an inline4 rr bike, you take the timing cover off the right side, and can hear hissing from there it's getting past the piston/rings.

Im not sure how the decomp lever plays into this though, your going to hear air in the pipe due to the valve being held open a tad right? This is why the compression test may be more relevant? The manual gives a specific min service limit on the compression .. ? would love to know. What about removing the decomp mechanism for the test? The valve cover does not need to be on (don't think)

By vlad7890, Posted May 18, 2011

Why does the piston need to be TDC for this test? I put in 100 psi and lost 12 psi.

Because you will be losing pressure much faster from a small volume (combustion chamber) than from a large volume (displacement + combustion chamber) of compressed air. You could do a leak down test in BDC but the acceptable loss guidelines would have to be adjusted for that.

Another reason used to be because of unplated cylinders where cylinder wear was worse at the top of the stroke than at the bottom. But I don't think with plated cylinders it makes any difference, they wear very little compared to the wear on the piston and rings.

By GoBollzD33P, Posted May 18, 2011

i just got a leak down test and my piston it is at 20% right now... yes time for a change asap!!

By Shawn_Mc, Posted May 18, 2011

I guess if you took the cam chain off and were certain both the valves are closed you could do it with it at BDC instead of TDC.

One of the things you look for during a leak-down is the leak location. You do this by listening.

A 20% leak in a single cylinder engine makes me think there's a problem with the test.

And a true leak-down is done with a leak down tester. One gauge has the amount of air available to the tester, the other gauge shows a percentage of the leak.

By MELK-MAN, Posted May 18, 2011

i just got a leak down test and my piston it is at 20% right now... yes time for a change asap!!

maybe, but as Shawn indicated.. where is it leaking ? (most) Past piston/rings or past the valves? If you hear the hissing sound of leaking air in the muffler, it's getting past the valves. At 20% i don't know how it would run at all, or with any power.. that is likely the decomp mechanism holding the valve open a bit?? I have never done one on a crf450 or single..

By GoBollzD33P, Posted May 18, 2011

we actually didn't really listen as to where the air was coming but the guy who did it suspects it's getting past the valves and piston since that's where the main area where air sounded like it was coming out of... he said i can actually still use the bike but i'm losing 20% of my power so i need to get my top end changed and broken in asap.

By bearscare, Posted May 18, 2011

I guess if you took the cam chain off and were certain both the valves are closed you could do it with it at BDC instead of TDC.

One of the things you look for during a leak-down is the leak location. You do this by listening.

A 20% leak in a single cylinder engine makes me think there's a problem with the test.

And a true leak-down is done with a leak down tester. One gauge has the amount of air available to the tester, the other gauge shows a percentage of the leak.

I'm not sure whether this is a fair (correct) test, I had the carb off the head

the left side case off and the header off. Air was being pushed out of the intake of the head and air was being pushed through the crank and coming out of a tiny hole in the spindle of the flywheel. There was no oil because I had just pulled the cylinder off and checked it and the piston for wear. I imagine if I did the test after the engine was on for a few minutes I would have probably had a better seal. I think that's what you do for a compression check. I'm not sure if a dry leak down is accurate.

I replaced the rings since I was down there. The cylinder still looked good cross hatch still visible.

I would have done the test at TDC if there was a way to stop the piston. I buggered up the allen screw on the crank trying to force it to TDC. So how do you hold it at TDC?

By MELK-MAN, Posted May 18, 2011

we actually didn't really listen as to where the air was coming but the guy who did it suspects it's getting past the valves and piston since that's where the main area where air sounded like it was coming out of... he said i can actually still use the bike but i'm losing 20% of my power so i need to get my top end changed and broken in asap.

i don't understand why you would not determine where the leak would come from.. im guessing one of the timing check screws could be removed to hear air escaping past the rings, and listening in the muffler is well.. so easy to do i again don't know why it wasn't done. Isn't it possible the test was done at the part of the stroke where the decomp slightly opens the valve? thus you could (emphasis on could) have way less than 20% actual leak. I just have never heard of a motor that was actually running worth a crap that had that kind of leak down.. as SHawn already pointed out, something isn't "adding up". Get a proper leak down test done by someone that knows enough to listen for leak from valves and/or piston..and has the correct test gauges (plural-2 gauges)

I would do a compression test, again.. when you do a leak down, it is pretty much standard procedure to do a comp test. Takes like, 2 minutes?? Almost no cost.. 78psi is hte min spec on an o4, bit lower for 03 and earlier that had the lower comp piston.

I'm not sure whether this is a fair (correct) test, I had the carb off the head

the left side case off and the header off. Air was being pushed out of the intake of the head and air was being pushed through the crank and coming out of a tiny hole in the spindle of the flywheel. There was no oil because I had just pulled the cylinder off and checked it and the piston for wear. I imagine if I did the test after the engine was on for a few minutes I would have probably had a better seal. I think that's what you do for a compression check. I'm not sure if a dry leak down is accurate.

I replaced the rings since I was down there. The cylinder still looked good cross hatch still visible.

I would have done the test at TDC if there was a way to stop the piston. I buggered up the allen screw on the crank trying to force it to TDC. So how do you hold it at TDC?

I agree with you, it wasn't a really fair test for your motor. You need to do a leak down test on a warm motor, that has oil. Oil is held in the cross hatches of the cylinder walls (that's what cross hatching is for..) thus your not getting as good a seal on the rings allowing more leak than normal. Another reason i think the "dry build" method is bullpucky.. The ring will simply scrape ANY excess oil up or down upon priming the oil pump. You are at least left with the protective oil within the cross hatching as the engine is designed to provide. The rings will break in just fine on the 'high spots' of cross hatching. THis is why its so important to "deglaze" or hone when rebuilding.. so sufficient oil can be held in the crosshatching.

I'm not sure how to hold it at tdc on this motor, i have yet to do a leak down on a crf450.. only compression tests and im throwing piston/rings at it every 150-200hrs or so. would be easier to get it ther with the spark plug out though..

By GoBollzD33P, Posted May 18, 2011

our leak down tester was a mac so i'm quite positive it was a sufficient tool... the hissing we could hear was very loud so we didn't have to put our ears against anything to hear.. but no we did not do a compression test at the same time either.. i already have my new top end parts so regardless if my old stuff is in good condition i'll keep them as spare parts.. or is that a no no?

By MELK-MAN, Posted May 18, 2011

our leak down tester was a mac so i'm quite positive it was a sufficient tool... the hissing we could hear was very loud so we didn't have to put our ears against anything to hear.. but no we did not do a compression test at the same time either.. i already have my new top end parts so regardless if my old stuff is in good condition i'll keep them as spare parts.. or is that a no no?

Once you have them off, a good mechanic with mics will be able to determine if the cyl, head and piston was in need of changing, or if it would have saved you money to have done a compression test (still not sure why this was not done). And just because you had an expensive leak down kit, it is still suspect if the leak down test was done right.. (just because you have a fender stratocaster doesn't mean ya can play like Stevie Ray Vaughn.. .

Not sure why your not looking at stuff before ordering parts either.. When you say top end parts.. from the crank up? or just a piston/rings..

i sold the 04 head ($85) and the high hour cylinder ($80- posted a pic of it in a thread recently about Rotella oil). Both work fine, i just felt they had sufficient hours to warrant replacing. The head was purchased and they did the seats, works great. The cyl was still in spec .. I would never have put these parts back on my bikes, but im not worried about spending $$ on new parts. You need to decide if it is worth more to you as a spare, or if it is in decent engough condition to sell to someone as a used but working part..or just throw away.. your budget will determine this.

By SkyHarborCowboy, Posted May 18, 2011

Am I missing something here but why isnt the piston placed at TDC before even applying pressurized air into the combustion chamber to do a leakdown test?

I dont know if the CRF's have an offset crank centerline and how that would effect the ability of the piston to stay at TDC when a pressurized source is applied to it. In the many leakdown tests I have done on engines I have always sought TDC and applied the air in increments and never had a tough time adjusting the crank to get the piston to hold at TDC without any type of stop.

By SkyHarborCowboy, Posted May 18, 2011

Hi-

I've been trying to do a leak down test and when I pressurize the cylinder to 100 psi I can't get enough torque on the allen screw on the crank to pull the piston to TDC. How does anyone do these test without having the crank (piston) move?

Thanks

Bruce

Your piston, rod and crank pin need to be in complete alignment. Off even slightly at it will turn on you. You also need to do your test at TDC in my opinion. That is where the greatest wear tends to be on the top half of the cylinder wall as the most pressure is excerted on the wall by the rings due to the greatest amount of combustion pressures.

Hissing at the Exhaust pipe (Exhaust Valves Leaking) Hissing at Carb (Intake Valves Leaking) Hissing at Crank Breather (Rings/Cylinder Wear). You can confirm the latter by squirting some oil in there and see what happens to your leakdown rate as the oil will help seal the rings and wall but there really is no need to.

Joe

Joe

By GoBollzD33P, Posted May 18, 2011

we didn't compression test because we didn't have one on hand.. keep in mind i didn't take my bike to anybody to get this done just a guy at my shop bought one off the mac truck and was trying it out.. even if it is off just a bit.. better to be safe than sorry. by top end i mean piston, rings and pin, when i bought the motor last year the guy said it was all rebuilt with top of the line components but i don't know if he was lying about the hours on it or not... so when i get the motor torn apart i will know for sure and report back.. i will also post up pics of my old stuff to make sure it is keepable or sellable... regardless of condition i want a fresh top end into my motor so i personally know hows many hours is on it and can take proper care for it from the start

Jeremy Martin Leads the Charge for Wiseco Riders at Daytona Supercross
Christian Craig Turns in Career Best in 450 Competition
MENTOR, Ohio (March 13, 2018) – Jeremy Martin showed the way for Wiseco-sponsored riders in Saturday night’s Monster Energy Daytona Supercross presented by Honda. In a season marred by bad luck and misfortune, Martin put together a near flawless ride to earn his first Eastern Regional 250SX Class podium finish of the season.
Martin qualified eighth for the division’s annual visit to the World Center of Racing, finished fourth in his heat race, and came home second in the 250SX main event, missing his first win of the year by less than a second.

“It’s Daytona, a real man’s track.” said Martin who sits fourth in points. “It was the toughest race of the year as far as fitness. I had to slow down a little bit, halfway through the main. I was getting close to (race winner) Jordon (Smith) and I was starting to think about where I could make a move on him, then I made some mistakes and he got away from me. Couldn’t quite get close again, but it’s good. We’re on the podium and in contention for wins again. That’s something I haven’t been able to say in supercross in a while. We want to get wins and now we know it’s coming.”
Martin’s podium was a bright spot, but the rest of the event was rough for the GEICO Honda/Factory Connection squad. RJ Hampshire crashed hard in his heat race and had to be transported to a local hospital. He injured his back and ribs, but shoulder pain left him with the most concern.
“I felt good on the bike all day,” said Hampshire via his Instagram account. “Had some pretty good speed and my foot just slid off hitting my shifter in those rollers during that heat race. After seeing the pictures from the crash I’m very thankful I didn’t take a shot to my head. I have some fractures in my T3/T4 in my back and ribs. Also have some damage to my lungs which is why I’ll be spending a couple nights in the hospital. I’ll be getting some more checkups this week on the shoulder also.”
Cameron McAdoo, the third member of the team, was unable to compete at Daytona after being sidelined with a hand injury two races ago in Atlanta.
Across the paddock, in the premier 450SX Class, Christian Craig got the call to fill in for Team Honda HRC. With the team’s regular riders Ken Roczen and Cole Seely out with injuries, it was up to Craig to carry the load for the factory team, and the upstart rider didn’t disappoint.
The San Diego native was solid in both qualifying sessions, won his heat race and snagged the holeshot in the division’s main event. After relinquishing the lead to eventual winner Justin Brayton, Craig continued to show he was up for the challenge. The 26-year-old rider raced for second and third for most of the 20-minute-plus-one-lap feature before losing one more spot in the late goings to bring his No. 32 Honda CRF450R home fourth in the final rundown.

“I had a great week testing with the team,” commented Craig. “They came down to Florida right after Atlanta and I feel like we really improved. Just getting more time on the bike and getting more comfortable was huge. I started off race day feeling really good. My qualifying position didn’t really show it, but overall I was happy with my riding. It’s all about having fun out there, and man, that’s what I did tonight. I was up front in the heat race, fell to third, but then the two guys in front took each other out so I ended up winning. You can call it luck or whatever, but I just put myself in a good position to capitalize on people’s mistakes."
“I had a good gate pick and some confidence going into the main. I grabbed the holeshot and led for almost the first lap, but [Justin] Brayton got by me pretty quick. I stayed second for quite a while. I just rode my hardest and did my best. Unfortunately, a couple guys got by me so I ended up fourth. The track was so tough. This is only my second time racing Daytona and last year didn’t go well, so I really wanted to get some revenge this year. It’s better than the week before, but man, I was so close to a podium. I just need to keep putting myself in good positions and work on getting better each weekend.”
Monster Energy AMA Supercross rolls on this weekend when the series visits the “Gateway to the West” for its annual race at the Dome at America’s Center in St. Louis. The 11th of 17 races on the 2018 supercross calendar will be televised live on FS1 Saturday, March 17, beginning at 8 p.m. Eastern Daylight Time, 5 p.m. Pacific.
-30-

I have a 03 450 that I just got and it runs great! I love my bike and am big on preventative maintenance. I have searched the threads on TT and have not found any descriptive threads on how to check valve clearance or adjust them. Just by looking at them, I can see that the intakes need to be shimmed and the exhaust valves can be adjusted quite easily unless one needs to be adjusted differently than the other.
I tried to do it last night, and lined up the marks on each side to get the piston to TDC to check adjustments and could not get any readings on tolerances on either the intake nor the exhaust. I moved the crank a little bit forward and got a .011 reading on the exhaust valves. I read in a thread that the spec was .011" for the left one and .014" in the right for the auto decompressor. The spec I am using for the intakes is .006" Are these specs correct? :excuseme:The only issue is that the adjustment for the exhaust valves is one and the same. Different from my KTM where you can adjust each valve individually.
No matter where the cam was on the intake valves, I could not get any readings. Does anyone have a thread, website, downloadable manual, or article on checking and adjusting valves in these beasts?

I am selling my 2007 Honda CRF 450-R which is set up for desert racing (Track/desert). It has an 18" rear tire with a heavy duty setup (see description for details). The bike screams and has a Tokyo mods carb mod with the 10x ignition mapping (currently set to a handlebar switch for smooth power and max power). Gas tank is a 3.2 gallon IMS dry break tank. V4 steering stabilizer included. Precision Concepts suspention, Bike is set up for 6'4" 175lb rider. Zero oil leaks and well maintained using a preventative maintenance method with the best new parts each time. Receipts for all items can be provided. About 20 hours on the rebuilt head. Carb just rebuilt. Starts cold in just 2-3 kicks. 100% reliable bike as long as you turn the gas on. Current CA Red sticker and original title.

I recently replaced water pump and seal after I noticed that my '02 CRF450R was spilling coolant on easy trail rides. After the water pump swap (which was successful), I noticed the same problem. It's interesting - the bike only spits coolant (I mean a LOT of coolant) after passing anything above 1/2 throttle. The bike makes this weird 'gurgling' noise, like trying to suck through a straw when your glass is almost empty. This is weird because I properly bled/ burped the radiators with coolant, and filled them to normal operating levels. The coolant spills through overflow hose.
anyways - I swapped the radiator because I thought maybe the bike was running hot. I purchased oversized radiators, bought a 1.6 radiator cap (with a temp gauge) and bought engine ice. The bike runs very very cool - the temp gauge allows me to see this. Still, the bike shoots coolant out of the overflow after going above half throttle, making the same weird gurgling noise when it does. Bike has all of its power, top end was replaced not too long ago.
I'm lost and don't know what is wrong with the cooling system in my bike. How do I make the bike stop shooting out coolant, and stop making the weird gurgle noise??? Any advice would help me!!! Thank you!